THERE IS a lot Congress could do to better protect U.S. elections, and a lot Senate Majority Leader Mitch McConnell (R-Ky.) has not allowed lawmakers to achieve. Now, two senators are offering one more opportunity.

Sens. Chris Van Hollen (D-Md.) and Marco Rubio (R-Fla.) are urging colleagues negotiating this year’s defense spending bill to include an amendment in that legislation that they believe would make Russia less likely to repeat its 2016 interference. The provision would mirror parts of the duo’s stand-alone Deter Act, and it also would build on a proposal tacked on to a version of the reauthorization act the House passed last month.

The senators’ Deter Act idea differs from its House counterpart in a few ways, the most important of which is that it is more carefully targeted actually to deter. The House bill would impose additional sanctions on Russia’s sovereign debt immediately and make them difficult to remove. Mr. Van Hollen and Mr. Rubio instead suggest readying sanctions that would take effect in the event of future interference. It’s a smart strategy.

Any state that considers taking aggressive action against another weighs the potential costs against the gains. The U.S. response to Russian malfeasance has not been consistent or credible enough to change Vladimir Putin’s calculus. President Trump’s sternest reprimand to the Kremlin leader has been a smirking “ Don’t meddle,” so altering the equation is up to Congress. The House bill would make Russia suffer now, no matter whether it decides to attack again, and the bar for removing sanctions is so high that the country has no guarantee of relief even if it does not. Mr. Van Hollen and Mr. Rubio, on the other hand, would give Russia a clear reason to refrain.

The senators’ suggestion has another advantage: Because there is a small stock of sovereign debt available, they would include a panoply of other punishments, including blocking transactions with Russia’s energy, banking and defense sectors, as well as sanctioning oligarchs and other figures participating in any interference efforts.

Mr. McConnell can marshal arguments against other essential bills he has blocked, besides the worry that they might offend the president. Rules requiring robust disclosure on online ads, some Republicans say, are campaign finance reform in disguise. Proposals to beef up electoral cybersecurity or back up the process with paper ballots, they claim, constitute federal overreach into a state-led realm. These are substantive, even if not terribly convincing. But there is no excuse for refusing to punish a country that attacks U.S. democracy and every reason to put deterrence in place so it doesn’t come to that.

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